Asphalt-surfaced roadways are built to facilitate vehicular travel. Depending upon usage density, base conditions, temperature variation, moisture levels, and/or physical age, the surfaces of the roadways eventually become misshapen and unable to support wheel loads. In order to rehabilitate the roadways for continued vehicular use, spent asphalt is removed in preparation for resurfacing.
Cold planers, sometimes also called road mills or scarifiers, are used to break up and remove layers of an asphalt roadway during a resurfacing operation. A cold planer typically includes a frame propelled by tracked or wheeled drive units. The frame supports an engine, an operator's station, a milling drum, and conveyors. The milling drum, fitted with cutting bits, is rotated through a suitable interface with the engine to break up the surface of the roadway. The broken up roadway material is deposited by the milling drum onto the conveyors, which transfer the broken up material into haul trucks for removal from the worksite. A paving machine follows behind the cold planer at a desired distance and covers the milled surface with fresh asphalt. Haul trucks carrying fresh, hot asphalt from a plant periodically pass between the paving machine and the cold planer to deliver additional asphalt to the paving machine. This process repeats until the resurfacing operation is finished.
After its production, fresh asphalt gradually cools until it is eventually laid onto the milled roadway surface. If too much time passes between its production and its use on the roadway, the fresh asphalt can cool to temperatures at which it becomes brittle and unworkable. Thus, supervisors of a resurfacing operation may wish to coordinate deliveries of fresh asphalt with actual rates of asphalt usage by the paying machine to minimize cooling time and wasted asphalt. However, when the cold planer ahead of the paving machine stops during operation, such as to wait for an empty haul truck or when cutting bits on its milling drum need replaced, the paving machine may be required to slow or stop its operations, during which time the fresh asphalt may fall below its usable temperature.
One attempt to coordinate milling and paving operations is disclosed in U.S. Pat. No. 7,549,821 B2 that issued to Hall et al. on Jun. 23, 2009 (“the '821 patent”). In particular, the '821 patent discloses a pavement recycling machine for breaking up used pavement from a surface, mixing the broken-up pavement with other materials, and reapplying the mixture to the surface. The machine includes a frame that supports an engine for powering a hydraulic system. The hydraulic system drives traction devices for moving the machine and rotary mill heads for breaking up pavement on the surface of a roadway. The broken-up pavement may be mixed with rejuvenation materials and/or supplementary aggregate materials before being dispensed via an outlet onto the surface of the roadway, leveled, and tamped. A closed loop control system having a number of sensors monitors and controls operating parameters of the machine based on parameter set points and feedback signals from the sensors. The sensors generate signals indicative of the machine position, machine speed, position and rotational speed of the rotary mill heads, pavement temperature, rejuvenation material temperature, and screed settings.
While the system of the '821 patent may allow for some coordination of milling and paving processes, it may not be applicable to resurfacing operations having separate milling and paving machines and where fresh asphalt is prepared at a location away from the jobsite.
The control system of the present disclosure solves one or more of the problems set forth above and/or other problems in the art.